Electric motor simulation, from magnetic circuit to cooling jacket
Predict the torque, back-EMF and losses of your electric motor, the temperatures its windings and magnets reach, and the stresses in its rotor at top speed, before a prototype is wound.
An electric motor’s rating is a balance between three limits: the torque its magnetic circuit can produce, the temperature its insulation and magnets can stand, and the speed its rotor can survive. Push current up for torque and copper losses rise with its square. Push speed up and iron losses climb, the thin bridges that hold the magnets in an interior permanent magnet rotor carry more load, and the back-EMF approaches the voltage the drive can supply.
More about electric motor simulation
Electric motor simulation looks at each limit in turn and then together. Electromagnetic models give torque, torque ripple, cogging torque, back-EMF and the copper, iron and magnet losses at the operating points you choose. Those losses become heat sources in a thermal model of the stator, rotor, housing and cooling jacket. Structural models give rotor stresses at maximum speed and the natural frequencies of the stator and housing, which decide whether electromagnetic forces turn into noise.
Coupling the electromagnetic and thermal models matters here, because winding resistance rises and magnet strength falls as the motor heats up. A change to slot shape, magnet pocket or jacket channel comes back modelled and ready to feed the motor’s detailed design, drawings and production.
Typical machines: traction motors, servo and robot joint motors, pump, fan and compressor motors, generators, in-wheel motors and motors for drones and e-bikes.
What a motor study tells you
What torque will it produce?
Average torque, torque ripple and cogging torque across the current and speed range, for the winding and magnet design in the model.
What back-EMF does it generate?
The back-EMF waveform, its constant and its harmonic content, so the voltage needed at top speed is known before the drive is specified.
Where do the losses come from?
Copper losses in the windings, iron losses in the stator and rotor laminations, and magnet losses where they matter, at each operating point.
How hot do the windings and magnets get?
Hot spot temperatures in the slots and end windings against the insulation class, for example 155 °C for class F, and magnet temperatures against the grade’s limit.
Is the rotor safe at top speed?
Stress in laminations, magnet bridges, sleeves and the shaft at maximum speed and overspeed, with the fit between rotor and shaft included.
Will it be noisy?
Natural frequencies and mode shapes of the stator and housing, set against the electromagnetic force orders at your running speeds.
What we model
Electromagnetic performance
Models of the stator, rotor, magnets and windings giving flux density, torque, back-EMF and inductance at the rotor positions and currents you choose.
Loss prediction
Copper, iron and magnet losses at each operating point, passed to the thermal model as heat sources.
Winding and magnet temperatures
Conduction through windings, slot liners, laminations and housing, with the contact between stator and housing represented.
Cooling jackets and channels
Spiral and axial water jackets, oil channels and shaft cooling compared on temperature, flow distribution and pressure drop.
Air-cooled and enclosed motors
Fan-cooled and totally enclosed designs, with external fins, internal air circulation and end winding cooling in the model.
Rotor stress at speed
Centrifugal stress in laminations, magnet bridges and retention sleeves, including interference fits and thermal growth.
Stator and housing vibration
Modal and harmonic analysis of the stator, frame and mounts, with loads from the electromagnetic study applied to the structural model.
Before you start
What to send us
- CAD of the stator, rotor, magnets, windings and housing (STEP or native), or lamination drawings
- Winding layout, turns per coil, slot fill and connection
- Lamination steel and magnet grades, with material data if they are uncommon
- Operating points: current, speed and drive voltage limits, plus the duty cycle
- Cooling arrangement, coolant flow and inlet temperature, or the fan details
- Maximum speed, overspeed requirement and any noise or vibration targets
How does rotor speed affect stress?
Steeply. In a thin rotating ring, hoop stress is σ = ρω²r², so doubling the speed quadruples the stress. Magnet bridges and retention sleeves are usually where that shows first.
Why do magnet temperatures matter so much?
Neodymium magnets lose remanence and coercivity as they heat up, so torque falls and the risk of irreversible demagnetisation under high current rises. The magnet temperature sets how hard the motor can be driven.
Can you work from lamination drawings only?
For the electromagnetic model, a lamination drawing, stack length and winding data are often enough. The thermal and structural studies need the housing and cooling details as well.
How does this differ from a powertrain study?
A motor study concentrates on the machine itself. A powertrain study looks at the motor alongside the battery, inverter and shared cooling loop, and either can lead into the other.
Send us your motor
